Oil refineries, pipelines, chemical plants and other facilities that require the transport of fluids can have miles of interconnected pipes and tubing. As fluids are caused to go from one operation or outlet to another, pipes must be fitted with various fittings, connected to various outlets and devices, and connected to other pipes and tubing. Oil refineries are archetypical of the wide range of ways in which such connections can be arrayed.
In an oil refinery, hydrocarbon fluids are often sent from process to process under varying pressures and flow rates. Thus, it is not uncommon to incorporate miles of pipes in a range of diameters. Some sections of such pipe can exceed six feet in diameter while others are far less than a one foot in diameter. Typically such pipes are made of thick steel or iron. Connecting these pipes to the various devices that will receive the fluids is most often accomplished by butting a flanged end of one pipe to a flanged end of another pipe or device. The two flanges are then usually bolted together.
Maintenance of a unit to which a pipe is connected or to a pipe itself ordinarily requires one to unbolt the flanges and separate the pipes. It is a common practice to place a blind or blank over the end of the pipe or vessel that will not be involved in the maintenance. The blind is usually bolted to the flange on that pipe. This prevents fluid that is flowing through that pipe from spilling or leaking and prevents contaminants from entering the pipe. Unfortunately, current practice does not provide for preventing the spillage of fluids that is present in the lines prior to the insertion of the blind. Determining whether or not fluid is in such a line and will spill out upon disconnecting of the flanges is primarily a matter left to guesswork. Poor judgments in this regard can result in environmental mishaps.
One might suspect that placing a collection pan under the potential spill could assist in avoiding such spills. However, the amount of draining fluid, the awkwardness of the method, and potential impact of other factors such as wind gusts show that such a technique is still subject to considerable error. Furthermore, pipes and other vessels sometimes carry fluids under pressure. Simply disconnecting such a pipe would result in that fluid being spewed out of the pipe juncture. This could injure workers and/or release toxic materials into the environment. Add to this the trend in environmental laws and regulations to strictly limit the amount of leakage or spillage that can occur and one can see the impetus for a new technique. Where small spills of material such as oil and other hydrocarbons may once have been acceptable this is no longer the case. Even very small spills must typically be reported to governmental agencies, often under the threat of sanctions.
Double-containment strategies have been used generally to contain pipes and other vessels. Essentially, these systems consist of a housing or outer pipe that is fitted over the pipe that may leak. These systems are designed to encase entire sections of pipe without regard for one's ability to perform maintenance on the pipe or its fitting. They are designed to contain spills in static systems. That is, one must ordinarily remove the secondary containment device to gain access to a joint or other section of pipe. U.S. Pat. No. 4,930,544 describes a double-containment thermoplastic pipe assembly which encases a section of pipe to include fittings thereon. The device may contain leaks but is not designed to enable the performance of work at the junction of two joined sections of pipe or other vessel while containing fluids that would otherwise leak from them.
New methods and devices for avoiding spills and leaks from vessels while performing maintenance on pipes and vessels are in great demand. This is particularly true when such maintenance involves disconnecting pipe junctions or joints. Advances in this area would materially enhance the quality of the environment by preventing the air, water, and soil from being fouled.